This invention relates to a facsimile control apparatus for use in a frequency band compression facsimile receiver, and more particularly to a facsimile control apparatus for controlling the cutting of a roll of record sheet to a given length and the transportation of a record sheet thus cut.
A prior art frequency band compression facsimile apparatus, as shown by way of example in FIG. 1, is comprised of a transmitting mechanism section, and a receiving and recording mechanism section. Referring to FIG. 1, a plurality of originals 1 to be transmitted are stacked in a superposed manner in the transmitting mechanism section located below a one-dotted line as viewed in the drawing. The plurality of originals 1 are set with their information surfaces directed downwards, so that these originals will be separated one by one sequentially from the lowermost original by means of a separating roller 2 and transported in the direction of arrow by means of a transporting belt (not shown). A set of an original detecting light source 3 and a detector 4 is disposed in opposing relation to each other in an original transporting passage, so as to detect the presence or absence of an original at an original detecting position 5, thereby producing a sheet control signal as shown at A in FIG. 2. A level a.sub.I of sheet control signal A represents the absence of an original being detected in the passage (or an interval between a preceding original and a succeeding original), and a level a.sub.II is indicative of the condition of an original being detected.
Turning back to FIG. 1, original 1 past original detecting position 5 is subjected to irradiation of light from an illumination light source 6 and linearly scanned at a right angle with respect to the direction of shift of the original, so that an image of original 1 is converted to an image signal. Conversion of an original image to an image signal is achieved by means of a bundle of optical fibers 7 having a linear end and a circular end. The bundle of optical fibers 7 is disposed in the vicinity of illumination light source 6, with its linear end opposing the original surface at a right angle with respect to the direction of shift of the original, and with its circular end opposing a rotary scanning optical system 8, in a manner that the circular end may be scanned by rotary scanning optical system 8. As a result, the resultant photo-signal is converted to an electrical signal representing an image signal by a photoelectrically converting element 9. The image signal is schematically shown at B in FIG. 2. A level b.sub.I of image signal B is indicative of a signal containing no effective image signal, namely, a scanning signal scanning an area other than the original surface, and a level b.sub.II having a hatched duration represents an original surface scanning signal which contains therein an effective image signal. A signal for virtually discriminating level b.sub.I from level b.sub.II is an original signal shown at C in FIG. 2, which signal is prepared from sheet control signal A in the following manner.
In FIG. 1, a length l of transportation of original 1 from original detecting position 5 to a position, at which the original is linearly scanned by the bundle of optical fibers 7, is constant. Since the original transporting belt (not shown), in general, is driven by a pulse motor, an instant c.sub.I at which the scanning starts and an instant c.sub.II at which the scanning terminates, respectively shown at C in FIG. 2, are determined respectively by counting the number of pulses for running the pulse motor, respectively from the leading edge a.sub.III of sheet control signal A in FIG. 2 and from the trailing edge a.sub.IV of signal A. In other words, the length of delay time l.sub.C is determined by a given number of pulses corresponding to the distance l (the length of transportation of an original) shown in FIG. 1.
Among the signals shown in FIG. 2, sheet control signal A and image signal B are to be transmitted to the receiving side. Original signal C is not necessarily transmitted to the receiving side, because the original signal can be easily reproduced from the sheet control signal, as described in the above.
In a band compression facsimile of this type, a scanning line density signal d is also transmitted to the receiving side at every time of initiation of the scanning for each original, as shown at D in FIG. 2. These signals to be transmitted are encoded in the manner schematically shown at E in FIG. 2, and then transmitted to the receiving side. The way of encoding these signals is not a subject matter of the present invention, and hence no description is given further.
Turning back to FIG. 1, the receiving and recording mechanism section located above the one-dotted line will be explained. When transmission codes such as shown at E in FIG. 2 are received, there are obtained decoded signals F, G and H in FIG. 2 corresponding to signals A, B and D, respectively, by means of a decoder unit (not shown).
Reference alphabet F illustrates a sheet control signal, by which a record sheet feeding signal and a cutting signal are formed. The arrangement shown in FIG. 1 is in the case of an electrophotographic recording. In this embodiment, an electrophotographic record sheet is fed by a roll sheet 10, and the leading end thereof normally stands by at a cutting position 12 in a cutter 11. Insomuch as sheet control signal F (in FIG. 2) is at a level f.sub.I, roll sheet 10 remains stationary. When signal F is raised to a level f.sub.II, the roll sheet is rotated in the direction of arrow, so that the roll sheet is paid out by a given length through roll sheet feed roller 20. Simultaneously therewith, a record sheet 10' which has already been cut by a given length and transported to some extent in the preceding cycle is also shifted. In general, roll sheet 10, in some cases, is required to be stopped at a standing-by position even for a duration that record sheet 10' is being transported for recording. In view of this, it is necessary that pulse motors as driving power sources be separately provided. Alternatively, only a single power source may be used, while the drive of the roll sheet is controlled by means of a clutch 21. This apparatus is assumed of taking the latter means. In such a case, engagement and disengagement of a clutch can be accomplished by sheet control signal F in FIG. 2. More specifically, the clutch disengages at level f.sub.I, and the clutch engages at level f.sub.II. Level f.sub.II corresponds to level a.sub.II of sheet control signal A in the transmitting side. Thus, in response to the transportation of original 1 to be transmitted through original detecting systems 3 and 4, in the transmitting side, a record sheet is fed from roll sheet 10 via cutter 11 in the receiving side.
Let us now assume that the receiving side starts receiving an effective image signal of image signal G which is contained in a hatched area and represented by a level g.sub.II with a delay time l.sub.G after the leading edge f.sub.III of sheet control signal F. A level g.sub.I of signal G and said hatched area (duration) g.sub.II of signal G correspond to levels b.sub.I and b.sub.II of image signal to be transmitted as shown at B in FIG. 2. At this instant, record sheet 10' is already charged uniformly through a charger 13, and the leading end of record sheet 10' has reached a recording position 14 at which the scanning for record is to be effected. The distance from cutting position 12 to recording position 14 is equal to the distance l from original detecting position 5 to the scanning position in the transmitting mechanism section.
The image signal G (hatched portion) thus decoded is converted to modulated light 16 by means of a light-modulator 15, such as a modulation laser, a glow tube, or a modulator of an external modulation type using such as a crystal. The modulated light 16 enters a rotary scanning optical system 17. A bundle of optical fibers 18 is linear at one end and circular at the other end, likewise the bundle of optical fibers 7 shown in the transmitting mechanism section. This circular end of optical fibers 18 is scanned by rotary scanning optical system 17. Accordingly, at the linear end of optical fibers 18 a scanning light which is subject to intensity modulation in response to the image signal contained in the level g.sub.II of image signal G in FIG. 2. The scanning light thus obtained scans the surface of record sheet 10' which is transported opposite to the linear end of optical fibers 17 and in the direction perpendicular to the linear end. Consequently, an electrical resistance is lowered in the portion exposed to light on the record sheet surface 10' to cause discharge of electric charge charged beforehand, whereby a latent image inverted due to electrostatic charge is formed on the record sheet surface. Image signal G in FIG. 2 contains a synchronizing signal representing the end of a scanning line, which is to be described later, and generates a record sheet transporting signal in synchronism therewith. The record sheet transporting signal is applied to a drive system using a pulse motor so as to transport intermittently record sheet 10' which is already cut in accordance with the aforesaid synchronizing signal. Record sheet 10' having thereon a latent image passes through a developing unit 19 containing therein toner, whereby the latent image on the record sheet is developed into a permanent visible image.
The trailing edge f.sub.IV of sheet control signal F generally occurs within the hatched duration of image signal G, namely in the midway of the effective image signal represented by level g.sub.II. The trailing edge f.sub.IV of this signal corresponds to the trailing edge a.sub.IV of sheet control signal A in the transmitting side, and the record sheet cutting position 12 in the receiving side corresponds to the trailing end of the transmitted original. Thus, a cutting signal is generated in response to the trailing edge f.sub.IV of sheet control signal F, thereby allowing the cutting of the roll sheet. A latent image is produced on cut record sheet 10' corresponding to a transmitted original image in the manner described above and then the cut record sheet 10' having the latent image is delivered via developing unit 19, a pair of squeeze rollers 20 and a drier (not shown) to the outside of the apparatus.
An image signal I in FIG. 2 representing an effective portion of image signal G is not always necessary for achieving the record of an image, but it is easy to reproduce image signal I from sheet control signal F in FIG. 2. The way of reproducing such a signal is quite the same as that for preparing signal C from sheet control signal A, and hence no description is given.
Regarding a line density, a line density signal h appears at every initial stage in each effective portion (hatched duration) of image signal G as shown at H in FIG. 2. Line density signal h is stored for the purposes of recording an image as well as determining a length of transportation of a record sheet. It is clear from the above that, in the receiving side, the image recording position 14, namely the position at which a length of transportation of record sheet 10' due to an intermittent sub-scanning is determined is spaced apart by a certain distance from the position 12 at which roll sheet cutter 11 is disposed. This results in the difficulty of controlling transportation and cutting of a record sheet. Even at the time of engagement and/or disengagement of a sheet feed clutch, or even at the time of operation of cutter 11, the recording of the image signal is continued, and a timing of transporting a record sheet as well as cutting the roll sheet to a given length give a delicate influence on a recorded image, with a likelihood of causing a variation in length of sheet cut or the jamming of record sheet in the peripheral portion.
For example, a delay in transmission of a sheet feed torque at the time of engagement of a sheet feed clutch causes a variation in an amount of a record sheet to be paid out, coupled with the intermittent scanning, thus resulting in an increased or decreased record in the leading end portion of the record sheet, or resulting in an error in a cutting length of record sheet. Although, at the time of cutting the roll sheet, a sheet feed clutch becomes disengaged, and a sheet feed torque for roll sheet 10 terminates, the cutting of the roll sheet is not surely completed at a high speed, thus exerting an unwanted load on the record sheet transportation, leading to a variation in scanning for record. A further difficulty has been experienced with the case where the originals are scanned with little or no interruption in the transmitting side, and image signals are transmitted successively to the receiving side. Fundamentally, the sheet feeding operation in the side of roll sheet 10, immediately after the termination of the cutting of the roll sheet, must be interrupted for a duration commensurate to a time gap between a previously transmitted original and a succeeding original to be transmitted in a subsequent cycle. Should the aforesaid duration be too short to disengage the clutch, or disengagement of the clutch be delayed, then the roll sheet would be unwantedly fed, despite of the closure of cutter blades 11. This causes an undesirable curl at the leading end of the roll sheet, and the curled leading end of the roll sheet would fail to pass through the pair of cutter blades, leading to the jamming in the peripheral portion. If a space between the pair of cutter blades 11 is increased in order to avoid the above problem, this increase would result in delaying the cutting operation. It follows that the aforedescribed problems occur.